Work holder for machine tools

ABSTRACT

The invention is an improved work holder embodying a dead center for use in the headstock of power tools such as grinding equipment. A dead center is provided in the form of a rod having a pointed end which is nonrotatable but retractable against a spring in a chuck. The chuck is provided with a rotating body having a faceplate mounted on a bearing in such a way that the end of the workpiece comes flush against the faceplate on the rotating member. In this manner, precision of concentricity with respect to the workpiece and precision with respect to linear dimensions is maintained in working on similar workpieces.

United States Patent m13,597,ss5

Ismael Gonzales 6457 Tokay Road, Tujunga, Calif. 91042 [21 Appl. No.757,060

[22] Filed Sept. 3, 1968 [45] Patented Aug. 10, 1971 [72] Inventor [54]WORK HOLDER FOR MACHINE TOOLS Primary Examiner-Wayne A. Morse, Jr.Attorney-Herzig & Walsh ABSTRACT: The invention is an improved workholder embodying a dead center for use in the headstock of power toolssuch as grinding equipment. A dead center is provided in the form of arod having a pointed end which is nonrotatable but retractable against aspring in a chuck. The chuck is provided with a rotating body having afaceplate mounted on a bearing in such a way that the end of theworkpiece comes flush against the faceplate on the rotating member. Inthis manner, precision of concentricity with respect to the workpieceand precision with respect to linear dimensions is maintained in workingon similar workpieces.

Patented Aug. 10, 1971 3,597,885

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WORK HOLDER FOR MACHINE TOOLS SUMMARY OF THE INVENTION The inventionrelates to an improved work holder for use in machine or power tools. Anexemplary form of the invention is described in detail herein adapted ina precision grinding machine.

The work holder of the invention basically is an improved chuckembodying a dead center adapted'for use in the headstock of the machine.The improved device embodies a retractable dead center, that is, a stemhaving a conical pointed end which can retract a limited amount into thechuck against a spring. Additionally, the improved device embodies arotatable faceplate mounted on a bearing on the device, the piece beingworked on when in position being held by the retractable dead center andflush against the rotatable faceplate.

The invention provides a solution to a problem in the art, and anappreciation of the nature of the improvement can be had from anunderstanding of the problem that it solves. A typical example of theproblem is found in the grinding of cylindrical parts in a precisiongrinding machine. For example, the part may be a generally cylindricalpart which might be a spool to be used in a sleevetype of valve. Thespool is to have spaced annular grooves ground or milled in it atspecified linear distances from the end of the spool. During grinding,

the concentricity must be held within rather precise tolerances and evenmore particularly the linear distances of the annular grooves from theend of the spool must be held within precise tolerances. When a numberof like parts are to be ground in this manner using previously knownequipment, maintenance of the required degree of precision in thetolerances was difficult and required repeated tedious attention to thedead cen ters in the headstock and tailstock of the machine,particularly that in the headstock, this being the end of the work towhich the rotative effort is applied. The dead center in previouslyknown types of equipment is, of course, subject to wear and impairmentin respect to precision in setting up the adjustments of the machinefrom one workpiece to another. A dead center is, of course, a centerthat does not rotate with the work. In the device of the hereininvention as stated, the dead center member which is in the form of acarbide rod retracts into the chuck in which it is mounted against aspring. Mounted on a bearing around the chuck is a member which carriesthe faceplate. Thus, when the workpiece is put in the machine its endengages the retractable dead center which retracts into the chuck withthe end of the workpiece coming flush against the rotating faceplate ofthe unit. Thus, concentricity from one piece to the next is maintainedby the dead center and the precision of the linear dimensions, that is,the dimensions of the annular grooves from the end of the workpiece aremaintained by the flush engagement of the end of the workpiece with thefaceplate of the device. Since it is mounted on bearings and rotateswith the workpiece there is no friction or impairment of the linearprecision from piece to piece. Thus, during the course of grinding alarge number of pieces a substantial amount of work and attention iseliminated because of obviating the need for constant rechecking andreadjustment to maintain the precision of the linear dimensions asdescribed.

A primary object is to provide an improved dead center unit capable ofsimultaneously maintaining precision with respect to concentricity ofworkpieces and also with respect to precision of the grinding or thelike at predetermined distances from the end of the workpiece.

A further object of the invention is to provide an improved dead centermember or unit for use in machines of the type described which ismounted to be retractable within a rotatable faceplate so that theworkpiece retracts the dead center and comes into flush engagement withthe faceplate.

Further object and additional advantages of the invention will becomeapparent from the following detailed description and annexed drawings,wherein:

LII

FIG. 1 is a partial pictorial view of a typical precision grindingmachine in which the invention may be adapted;

FIG. 2 is a sectional view of a preferred form of chuck embodying theinvention and adapted for use in the headstock of I a machine like thatof FIG. 1;

FIG. 3 is an enlarged sectional view showing the device of the inventionembodied in a machine like that of FIG. 1;

FIG. 4 is a view ofa modified form of driver plate that may be embodiedin the device.

Referring now to the various figures of the drawings, FIG. I is apartial view of a typical form of precision grinding machine. Themachine has a stand or base It) as conventional in this type of machinewith a table, platform or bed I2 at the top. Mounted on the machine is aheadstock assembly designated generally at 14 which embodies the usualdrive motor and power transmission means for delivering rotary power tothe chuck which is part of the headstock. Power transmission means areenclosed within the housings l6 and 18, the improved work holding chuckof the invention being designated generally at 20. The machine has arotary face plate 22 carrying dog 24 that engages the work for rotatingit as will be described.

The machine is provided with the usual manual adjustments for adjustingthe headstock assembly and tailstock assembly of the machine. Thetailstock assembly is designated generally at 30. In the tailstockassembly is a dead center member 32 and adjustment means are included asindicated at 34.

The machine shows a workpiece in position to be worked on as designatedat 36. As an example the workpiece may be of a type as previouslyreferred to such as by way of example a cylindrical member in the formof a spool to be used in a sleeve valve. Parallel annular grooves are tobe grounded into the workpiece. Numeral 40 designates a typical grindingwheel in a housing 42 and to which fluid is supplied through a pipe 44from a tank 46. Power for the grinding wheel is supplied by a motor 50through transmission means as designated at 52.

FIGS. 2 and 3 are cross-sectional views of the chuck in which theinvention is embodied.

FIGS. 2 and 3 show a preferred exemplary form of the invention whereinthe unit embodies a chuck in the form of a tapered cylindrical body 56,the left end having an external taper for insertion into a socket intowhich it is held. The body 56 has a bore 60, the end of which isthreaded as shown at 62. Received in this bore is the carbide rod 64which is the dead center having a conical tapered pointed end asdesignated at '66. The dead-centering rod 64 is urged outwardly by acoil spring 70 in the bore 60 which is held in position by screw plug 72in the threaded end of the body 56.

The dead-centering rod 64 has a transverse groove 76 in it that has aflat bottom as shown and engaging in this groove extending through asidewall of the body 56 is a set screw 78 which by engaging in thegroove prevents the dead-centering rod from rotating but allows it toretract a limited amount into the bore 60 as will be described.

The body 56 has a part 82 of intermediate external diameter an end part84 of smaller external diameter. Mounted on the diameter 82 is a rollerbearing 86 which seats against the square shoulder between the largerdiameter and the intermediate diameter 82 of the body 56. It is held inposition by a snap ring 90 that seats in an annular groove the part ofthe body 56 of intermediate diameter 82. Journaled on the hearing 86 isa rotatable cylindrical body 92 having a bore 94 and a smaller bore 96at the opposite end. The bore 94 is threaded at the end as designated at100 and received in this bore is a threaded closure member 102 andpositioned between this closure member and the bearing 86 is a flexiblescaling member 104 which may be of a conventional type. It should beunderstood that other types of seals may be used at this point in theunit such as O-ring type seals similar to those to be describedpresently. Such O-ring seal might be disposed in the bore of the closuremember 102.

Attached to the right end of the cylindrical body 92 is the faceplatemember 110. It has a bore 112 ofa size to be spaced radially from thepart of the body 56 of smaller diameter 84 and interposed between theseparts are a group of sealing O- ring 114. The member 110 has aeounterbore or another bore 116 of smaller diameter than the bore 112and positioned between the bottom of this bore and end of the body 56 isa sealing O-ring 120.

The member 110 has a flange part 122 that fits into the bore 96 in thebody 92 and the unit or member 110 has an extending flange 124 that fitsagainst the end surfaces of the cylindrical body 92 and is securedthereto by screws 126. The member 110 has a tapered end surface asdesignated at 128 and a flat end face as designated at 130.

Faceplate 110 is readily removable for substitution of other faceplatesto accommodate workpieces of different diameters and having end boresofdifferent sizes.

FIG. 3 shows the device mounted and positioned in the grinding machinewith the workpiece 36 in place. Mounted on the end of the workpiece is adog 140 secured to the workpiece by a set screw 142. The workpiece hasthe usual end bore 144 and tapered eounterbore 146 that receives theconical end 66 of the dead center rod which typically is made ofcarbide. Numeral 150 designates a drive rod extending between thedriving member and the dog 140 for rotating the work, this rod engaginga cylindrical lug 152 which is attached to the body 92 by way of a screw154 so that the entire body 92 and its faceplate rotates about thebearing as the workpiece is rotated.

ln setting up the machine for grinding, the headstock and tailstock areset to receive the workpiece 36 in the manner as shown. In setting up itwill be observed that initially the deadcentering rod 64 protrudes fromthe device as shown in FIG. 2 and when the workpiece is brought againstit and fitted to it, the dead-centering rod 64 retracts into its borewith the workpiece coming flush against the faceplate 130 of the body92. Thus, it will be observed that the end of the dead-centering rod 64preserves the concentricity as work proceeds from piece to piece. Thesetting of the chuck embodying the dead center in the machine determinesthe position of the end face 130, that is, the faceplate and therebydetermines the linear positioning of the workpiece in the machine andcontrols linear dimensions from piece to piece. Since the faceplaterotates with the workpiece there is no friction therebctween and noimpairment of precision of the dimensions that are ground in theworkpiece as the work proceeds from piece to piece. It is not necessaryto make new adjustments set up at intervals while grinding a lot ofparts or pieces.

FIG. 4 shows a slightly modified form of the invention embodying animproved way of holding the workpiece. In this form of the invention theparts are like those of the previous embodiment and similarly numbered,except that the end faceplate is provided with the circular screwdriverplate 135 having screwdriver projections 160 and 162. The end of theworkpiece is then provided with radial milled slots or grooves toreceive the screwdriver projections and 162, so that the rotation isimparted directly from the faceplate without the use of a dog. Theadvantage of this is that concentricity and linear tolerances can bemaintained without the use of a dog attached to the workpiece forrotating it, and the workpiece can be ground throughout its full lengthwithout having to turn it around to finish the grinding with a dogattached to a part of the workpiece.

From the foregoing, those skilled in the art will understand andappreciate the nature and characteristics of the invention and themanner in which it realizes and achieves the objectives as set forth inthe foregoing and the many advantages that are apparent from thedetailed description.

The foregoing disclosure is representative of a preferred form of theinvention and is to be interpreted in an illustrative rather than alimiting sense, the invention to be accorded the full scope of theclaims appended hereto.

What 1 claim is:

1. A work holder for holding a rotated workpiece comprising a chuck, adead-centering member having a pointed end and means mountlng saidmember 11'] said chuck so that It is axially retractable in a limitedamount and nonrotatable with respect to said chuck, rotatable meanshaving a faceplate concentrically mounted around said pointed end, andmounted relative to said chuck and said centering member, and mounted insuch a position that the workpiece engages against the rotatingfaceplate when the dead-centering member is axially retracted away fromsaid rotating faceplate.

2. A work holder as in claim 1 wherein said chuck has a bore, saiddead-centering member being mounted in said bore, and a springpositioned to tend to urge the dead-centering member outwardly in thebore.

3. A work holder as in claim 1 wherein said rotatable means comprises acylindrical member and bearing means interposed between said chuck andsaid cylindrical member.

4. A work holder as in claim 1 wherein said faceplate is configurated toprovide means to directly rotatably engage the end of the workpiecewhereby the work holder directly rotates the workpiece without aseparate dog.

5. A work holder as in claim 4 wherein said faceplate has radialprojection means positioned to be received in slot means formed in theend of a workpiece for directly rotating the workpiece.

6. A work holder as in claim 1 wherein said dead-centering rod has aside flat which has radial end shoulders and means extending through asidewall of said chuck engaging said fiat to prevent rotation of thedead-centering rod and to limit I relative axial movement.

7. A work holder as in claim 1 including means sealing the interior ofthe rotatable cylindrical member.

1. A work holder for holding a rotated workpiece comprising a chuck, adead-centering member having a pointed end and means mounting saidmember in said chuck so that it is axially retractable in a limitedamount and nonrotatable with respect to said chuck, rotatable meanshaving a faceplate concentrically mounted around said pointed end, andmounted relative to said chuck and said centering member, and mounted insuch a position that the workpiece engages against the rotatingfaceplate when the dead-centering member is axially retracted away fromsaid rotating faceplate.
 2. A work holder as in claim 1 wherein saidchuck has a bore, said dead-centering member being mounted in said bore,and a spring positioned to tend to urge the dead-centering memberoutwardly in the bore.
 3. A work holder as in claim 1 wherein saidrotatable means comprises a cylindrical member and bearing meansinterposed between said chuck and said cylindrical member.
 4. A workholder as in claim 1 wherein said faceplate is configurated to providemeans to directly rotatably engage the end of the workpiece whereby thework holder directly rotates the workpiece without a separate dog.
 5. Awork holder as in claim 4 wherein said faceplate has radial projectionmeans positioned to be received in slot means formed in the end of aworkpiece for directly rotating the workpiece.
 6. A work holder as inclaim 1 wherein said dead-centering rod has a side flat which has radialend shoulders and means extending through a sidewall of said chuckengaging said flat to prevent rotation of the dead-centering rod and tolimit its relative axial movement.
 7. A work holder as in claim 1including means sealing the interior of the rotatable cylindricalmember.